I have. For the moment, this object is ignored by Marketo. I have not even been able to map it as a custom object, probably because the SFDC API version Marketo connector is using does not render it. This means you will not been able to read it from Marketo, and even less update it.

I would recommend that, with regards to GDPR, Marketo be your source of trust rather than SFDC. and this is because the activity log provides you with information such as IP addresses on form fill out and cannot be tempered with.

Honestly at the moment I have to advise people using Salesforce and Marketo not to go down the road of the Individuals object. But it's quickly not cutting it. It has to be supported, and soon. But it definitely isn't right now.

We have been investigating the Individual object form strictly a SFDC perspective and for the moment it's added value is almost zero. It cannot be populated even from a SFDC web-to-lead form and it has no impact whatsoever.

It's an interesting step towards the unicity of the person, which is one of SFDC bigger weakness with regards to Marketing*, but for the moment, it's really limited and SFDC doc about it simply says that it will evolve in the future. The only way it seems you can make use of it is if you are using Pardot. I am not even sure that SFDC API enables you to access it...

-Greg

* Remember the lead object conception is dated back the the end of the 90's and was created in a time where a lead was converted into an opportunity or deleted, never recycled, and in which the first and last touche campaign were usually the same (which is why SFDC standard attribution model is last touch).